Single-Use Screws and Plates
Joanna Ford (R&D Officer, SMTL), Graham Yarlett (HSDU Manager, Royal Glamorgan Hospital), Gill Bailey (Contracts Officer, WHS), & Pete Phillips (Director, SMTL)
Small orthopaedic implants (such as screws and plates) that are prepared for, but not used during surgery, are often reprocessed hundreds or thousands of times. This has lead to concerns about the impact of reprocessing on implant quality. In addition, there are concerns over the legal implications of reprocessing implants, traceability of individual implants and contamination issues.
The aim of this report is to consider the scientific, clinical and practical issues associated with moving to sterile single-use orthopaedic implants.
This document discusses issues relating to reprocessed implants and compares them to pre-packaged single-use implants by addressing issues such as implant quality, compliance, compatibility of implants with instrumentation, cost, storage, training, management and supply. NHS Scotland moved to single-use implants in 2007 and feedback concerning their experience of this transition has been included.
It is common practice in many hospitals for unused metal orthopaedic implants such as screws and plates to be reprocessed by sterile services departments on multiple occasions (perhaps thousands of times) before they are actually used in a patient. However, little is known about the effect of reprocessing on implant performance
In 2006, the Scottish Chief Medical Officer (CMO) advised Chief Executives of the intention to move to a policy of using pre-packed, sterile, single-use small bone implants and other implants across NHS Scotland (Scottish Executive, 2006), initially focusing on orthopaedics. This policy was implemented in Scotland in December 2007 (Scottish Executive, 2007) and the deadline for implementation was the 31st December 2008. When NHS Scotland moved to using pre-packed, sterile, single-use small implants, they considered a number of issues of potential concern:
- The legal status of reprocessing unused single-use devices
- The effect of reprocessing on the quality of the devices
- Traceability of devices
- Contamination status of implantable devices
- The practicalities of switching to single-use pre-packed devices
Each of these issues is investigated in this report.
List of devices under consideration
A list of small orthopaedic implants that could be purchased as single-use items are shown below:
- plates/locking plates (including all large, small and mini fragment ranges)
- screws/locking screws (including all large, small and mini fragment ranges)
- K-wires/guide wires
- stainless steel wire
- external fixator pins and wires
- Steinman/Denham pins
- medullary nails and cross screws
- specialist screws i.e. cannulated screws
Current compliance with guidance
There are a number of issues relating to whether Trusts and their CSSD/HSDU comply with current standards and guidance.
Compliance with guidance
One issue is whether the reprocessing of a 'single-use' device is legal if the device has not actually been used in a patient. The MHRA DB2006(04) states:
'The reuse of single-use devices has legal implications: Anyone who reprocesses a device intended by the manufacturer for use on a single occasion, bears full responsibility for its safety and effectiveness' (MHRA Device Bulletin 2006(04)).
Some of the concerns raised about reprocessing single-use devices include:
- device damage or alteration
- inadequate cleaning and decontamination (for example, being unable to access all parts of the device)
- fatigue-induced failure
The guidance does not provide a definition for the term 'reuse', although it indicates that 'single-use' items should not be reprocessed in any circumstance.
Another relevant issue for reprocessed devices is whether each item should be individually traceable through the reprocessing system, which has not always been possible for small implants such as screws. European standard EN 13485 (BS EN ISO 13485, 2003), which is a specific standard for manufacturers of medical devices, states that:
'Sterilization records shall be traceable to each production batch of medical devices' (section 18.104.22.168)
'where traceability is a requirement, the organization shall control and record unique identification of the product' (section 22.214.171.124.1).
The problem with small reprocessed implants is that they are not always individually traceable through the system and it is not always possible to establish the batch that every small implant and screw originated from.
Moving to single-use pre-packaged items overcomes this problem, as items will remain in labelled packaging until they are used in a patient, therefore maintaining traceability and adhering fully to the guidance.
The impact of reprocessing - literature review.
In a letter the Scottish Executive wrote to all its Trusts, it was stated that
'there is evidence to suggest that reprocessed steel implants can cause inflammatory reactions to a much greater degree than pristine devices......there are also issues of corrosion and weakening caused by repeated processing' (Scottish Executive 2006).
When SMTL made inquiries to the Scottish Executive regarding their statements, they provided a series of photographs of reprocessed screws taken at high magnification, where surface damage was clearly evident (see figures appendix B), as well as a published paper about the corrosion of implants (Jacobs et al., 1998) which is discussed later in this section.
In order to further our understanding of the effect reprocessing has on implant performance, the PubMed database was searched (using keywords listed in appendix) in order to find information on the subject and the following section summarises relevant findings.
The mechanisms of metal corrosion
Jacobs et al 1998 published an in-depth review of the processes by which metal can corrode whilst in the body and how this can effect surrounding tissues and the body as a whole. The two main of types of corrosion are:
Once a metal implant is in the body, it is susceptible to electrochemical corrosion (the mechanism by which a metal has a tendency to donate electrons to an oxidizing agent in the body). Ions can also pass between different types of metals if they are in contact with each other, which causes what is known as 'galvanic' corrosion of the donating metal. Metals readily form a passive layer in a liquid environment which offers some protection from electrochemical corrosion, however all metals are at risk of corrosion once they are implanted in the body. Once this corrosion starts to occur, there is a danger that deeper metal layers will be affected and metal fracture can occur (Patterson et al., 2005).
Reprocessing involves the action of mechanical forces and contact with solutions and other metals. In theory, if reprocessing implants corrodes them mechanically (due to processes such as abrasion and fretting) and/or electrochemically (due to contact with solutions and other metals), there is the possibility that corrosion has commenced prior to implantation and once in the body, the metal may be further corroded due to previous metal fractures or a disruption of the passive layer. This, however is conjecture, as there is little published research that specifically demonstrates failure 'in-vivo' due to reprocessing.
In addition, if mechanical corrosion occurs during the reprocessing of an implant, one could speculate that this would increase the chances of electrochemical corrosion in the body and make metal fracture and subsequent implant failure more likely.
As well as the potential for implant failure, the degradation products of corrosion can elicit local tissue reactions such as inflammation around the implant. Jacobs et al., 1998. Systemic effects (such as metal ions reaching remote organs via the blood stream or lymphatic system) may also occur, although data for this is sparse.
The effects of device reuse on implant properties
There are many published papers describing implant failures and implant corrosion in the body. However, in the papers reviewed, no details about the previous history of the implant or the role of reprocessing in the failure are provided. Therefore, it is impossible to know if they were reprocessed many times before implantation and so it cannot be determined whether implant failure was due to corrosion by previous reprocessing or by corrosive forces in the body.
Magetsari and colleagues (Magetsari et al., 2006) carried out an investigation to compare the biomechanical and surface properties of new screws and plates with those which had been explanted from patients. Results showed that explanted implants failed stress tests more readily, were more hydrophilic and had rougher surfaces (hydrophilic surfaces may attract bacteria known to damage implants which bind readily to rough surfaces) (Gristina 1997). Microscopic observation also revealed pitting corrosion on the explanted implants and a different surface chemistry compared with new implants.
In summary, we have been unable to find published research that specifically investigates the effects of reprocessing on small orthopaedic implants in-vivo.
There are clearly theoretical risks for devices which have been reprocessed multiple times, which undergo detectable degradation, but it is not possible to link these with specific clinical incidents.
Pre-packaged implants should be assessed to ensure that they are of an appropriate quality i.e. that all companies should comply with the Essential Requirements of the Medical Device Directive and be appropriately CE marked.
Residual Contamination and Infection Issues
The contamination of small implants is possible when they are reprocessed alongside other items such as reusable medical devices that have biological tissue and fluids on their surface following their use in surgery. In addition, anecdotal information suggests that some implants are used for 'fit trials' and then not actually implanted but reprocessed (Christie, 2007). These are obviously contaminated when they go through reprocessing as they come into contact with body fluids and tissues at the point of use. It has been well documented that instruments can still have biological contamination on their surfaces following reprocessing (Sigler et al., 2005) and Scotland provided microscopic images of reprocessed screws with evidence of organic debris on their surfaces (see figure 3). Prions (such as CJD) are of particular concern as these proteins have the potential to cause disease and like other protein, can be difficult to remove (Department of Health, 2008). Visual inspection of instruments is not enough to ensure these instruments are clean (AAMI, 2003). It is possible that cross contamination could occur in the instrument tray, resulting in the transfer of contaminants to screws.
Sterilised, pre-packaged implants avoid the contamination concerns associated with implant reprocessing because once they are opened they will not be reprocessed.
Practical and Clinical Issues
The issue of compliance refers to whether the items prepared for an operation are considered to be suitable for use. In theatre, a judgement is made about whether instrumentation and implants that have been reprocessed are compliant with their criteria. If trays contain moisture or have tears in the drape that covers them, they are likely to be considered non-compliant and items are returned for reprocessing. In addition, if any form of contamination is detected on reprocessed items, they will also be returned. This is a common scenario in many hospitals and can incur considerable costs in the form of theatre cancellations, delays and return theatre visits, as well as the cost of repeated reprocessing. If single-use, pre-packed, implants are to be used for orthopaedic operations, this is likely to reduce the number of non-compliant trays. Experience in Scotland so far has confirmed this (personal communication). In addition, the companies who sterilise these single-use, CE marked items, are providing 'compliant' implants and the responsibility of ensuring compliance with the MDD and theatre requirements transfers from the Trust to the companies, along with any associated risk.
Compatibility of implants with instrumentation
The issue of compatibility between instrumentation and single-use implants from different manufacturers must be addressed before any single use implants are introduced. It would be recommended that an organisation investigates this issue in detail (for example, reviewing current instrumentation use in Trusts and discussing compatibility of specific items and instrumentation with manufacturers concerned) before making purchasing decisions.
Sterile, pre-packaged implants are likely to cost more than reprocessed implants (this has been estimated as 0-15% for the total costs involved). There are also the costs of additional storage, replacing existing stock, procurement and management changes that would need to be considered.
The cost of initially stocking theatres with the full range of pre-packaged items required is likely to be considerable. In addition, if pre-packaged items are dropped once they are opened in theatre, they cannot be used, so there is a potential for extra costs to be incurred.
Another potential issue is that some instruments may be on loan from the companies who supply the small implants used currently. Starting to use pre-packaged items may require the purchase of new instruments if they are from different manufacturers.
Introducing pre-packaged implants would eliminate other costs (such as reprocessing costs). The cost is ultimately dependent on the size of the item which is being processed and the methodology used for pricing CSSD services. For example, varying quantities of screws may be reprocessed in the same tray on any one occasion. The reprocessing of plates is likely to cost more due to their size.
Many costs associated with reprocessing items are 'hidden' and difficult to calculate. For example, trays are checked at different stages after reprocessing prior to use which costs staff time and many trays are returned from theatre for being considered 'non-compliant' which can incur considerable costs in the form of theatre delays and cancellations.
In addition, more efficient use of CSSD resources may be made by moving to this system, as it would allow CSSD staff to concentrate on more important issues, such as difficult to clean instrumentation.
Clearly, individually wrapped devices will take up more room due to the packaging which may be a problem for some organisations. Although some companies provide storage solutions, some of them make a charge for these systems. Storage solutions vary between hospitals and is dependent on the layout and potential space available
For example, a busy hospital with a number of orthopaedic theatres in use at any one time may find mobile trolleys work well to transport the implants between theatres. Storage solutions vary between hospitals and are dependent on the layout and potential space available.
Some organisations may find the quantity of items held in stock can be reduced considerably when a sterile single-use policy is implemented. The reason for this is that many hospitals keep a large variety of items on a 'just in case' basis.
Packaging & theatre preparation time
Sterile pre-packaged devices are individually double wrapped. One potential issue raised by one of the manufacturers was that more time may be required to individually unwrap each screw or small implant, compared with opening one tray with an array of items. However, communication with NHS Scotland indicates that although clearly more time is required to open the packs, once users are familiar with the items and new ways of working, it did not take considerably longer, and in their view, has not had any impact on theatre time overall. In addition, less time should be required to check items and trays prior to use. When small implants are reprocessed, every individual item should be inspected before being placed in theatre trays which is a time consuming process. If less items are reprocessed for any given operation and less trays used, the time required to check for compliance will be reduced, as well as the number of trays that are returned for further reprocessing due to non-compliance. This obviously has cost implications in terms of staff time saved.
Key to this is a review of working practice in theatres. There is likely to be an impact on theatre staff if they take on the management of stock as a result of moving to single-use items, which may be the case in some hospitals. Realigning stock levels and setting up an inventory is likely to take extra time at the beginning of the process, but when the system has been established, it is thought that it should not be a problem.
It is important that sufficient training is carried out prior to the implementation of pre-packaged, pre-sterilised implants. This had been managed internally in Scotland to ensure consistency and control. When selecting a screw of the desired size, it is sometimes helpful to visually compare it to other screws in the range (which is currently possible with reprocessed screws in racks). One of the implementors in Scotland confirmed that the product can still be visualised through the packaging for comparison prior to use and this has not been identified as a significant issue in Scotland. In addition, templates are available in order to compare items to help clinicians select the correct size implant.
There is a potential waste issue if pre-packaged products are dropped during operations as items will need to be discarded, or if they are 'tried for size' but do not fit and so are not used. Also, double-wrapped items use more packaging than reprocessed devices, and there is therefore an associated increase in packaging waste.
However, the reduction in reprocessing items means that there is the potential for saving other resources, such as water, electricity and other packaging used within CSSD.
One issue with reusable screws and small implants is that many of them are never used (especially those at the extremes of sizes), but continue to incur reprocessing costs as they are kept on trays on a 'just in case' basis. Although a small number of these sizes are still kept available as sterile pre-packed items, this wasteful reprocessing of rarely used devices would cease, leading to more efficient use of CSSD resources.
Management and supply
If hospitals decide to move to using pre-packaged, sterile, single-use small implants, it is vital that manufacturing companies and suppliers are able to cope with the increased demand.Some companies now supply the full range of pre-packaged sterilised items and others are working towards providing a larger range of these items (although it may be more advisable to purchase from more than one company in case of supply problems).
Scotland have also confirmed that they have been able to obtain replacement/additional devices usually within 24 hours.
Changes in procurement, budget management, stock control, storage and contract management all need to be taken into account when considering introducing pre-packaged single use implants.
In Scotland, sterile service units and theatres worked closely together at all stages of the implementation process. It was stated that in some ways, the new system of using pre-packaged sterile implants made ordering easier in that every time an implant package is opened, a label is available which is placed into a system which is then used to indicate what must be ordered. This system has proved to be simple and convenient.
The advantages and disadvantages of using pre-packaged single-use implants
Based on the above analyses, the following summarises the potential advantages and disadvantages of moving to single-use small implants:
- Full traceability of all implants.
- Guaranteed sterility.
- Adheres to guidance on the use of single-use devices.
- No residual contamination risk.
- No risk of implant corrosion or fatigue due to reprocessing.
- Transfer of risk from the NHS to industry as the quality and sterility of the implants are the responsibility of the manufacturer.
- A reduction in stock levels as only items required will be reordered.
- The risk of non-compliant trays being sent to theatre and returned to CSSD is reduced.
- The risk of screw racks being replenished with incorrect sizes/types will be eliminated.
- Cost savings are realised due to the elimination of the reprocessing of these devices.
- Time and resources are released for sterile service departments, allowing them to focus on other areas of decontamination and reprocessing, providing a more efficient and better quality service for the rest of the reusable instrumentation
- If storage is moved from CSSD to theatres, theatres are required to find storage for the trolleys/cabinets holding the single-use devices.
- Theatres may have to find some extra staff resource to deal with stock and procurement management.
- Sterile, single-use implants may cost more, depending on the manufacturer.
- There is the potential for procedures to take longer due to the extra time taken opening the individual packs.
- There may be a necessity for some clinicians to change supplier if the current supplier is unable to provide the necessary single-use devices.
The authors would like to thank Mark Higgins (Senior Charge Nurse, Aberdeen Royal Infirmary) and Jim Nelson (Theatre Manager, Edinburgh Royal Infirmary) for discussing their experiences of moving to single-use implants in Scotland and to Peter Christie, Senior Medical Officer, Public Health Professional Group Scottish Government Health Directorates for providing documents, contacts and advice. NHS Scotland kindly provided a number of images showing differences between new screws and reprocessed screws, and have given their permission to publish these images.
- AAMI TIR30:2003 . A compendium of processes, materials, test methods, and acceptance criteria for cleaning reusable medical devices . The Association for the Advancement of medical instrumentation . Technical Information Report . 2003
- BS EN ISO 13485. Medical devices-Quality management systems-Requirements for regulatory purposes . 2003
- Christie P . Enquiry response . Health Protection Scotland . 2007
- Department of Health Report. Report on prion inactivating agents . Engineering and Science advisory committee. August 2008
- Gristina A G . Biomaterial-centered infection: microbial adhesion versus tissue integration. Science : 237, 4822 ; 1588-95 . 1987
- Jacobs J, Gilbert J, Urban R. Corrosion of metal orthopaedic implants. J Bone Joint Surg Am. :80, 2 ; 268-82
- Magetsari R, Van der Houwen E, Bakker M, Van der Mei H, Verkerke G, Rakhorst G, Hilmy C, Van Horn J, Busscher H. Biomechanical and surface physico-chemical analyses of used osteosynthesis plates and screws--potential for reuse in developing countries? J Biomed Mater Res B Appl Biomater :79, 2 ;236-44. 2006
- MHRA Device Bulletin 2006(04). Single-use medical devices:implications and consequences of reuse. 2006
- Patterson S, Daffner R, Gallo R. Electrochemical corrosion of metal implants. AJR Am J Roentgenol :184, 4 ;1219-22. 2005
- Scottish Executive. Burns H. Migration to single-use pre-sterilised individually wrapped small orthopaedic implants in NHS Scotland. Letter by Scottish Executive, Health Department. 2006
- Scottish Executive, Health Department. Decontamination-migration to single-use pre-sterilised individually wrapped small orthopaedic implants. NHS Circular. 2007
- Sigler K, Chladkova K, Vacata V, Gebel J, Gaskova D . Process-independent quantitative assessment of residual biological contamination of medical devices reprocessed in washer-disinfectors. Folia Microbiol (Praha) :50, 3 ;239-46. 2005
APPENDIX A: Key words used for literature search
The following combination of terms was used to search for relevant publications on the PubMed database:
- Reprocessing/single-use/sterilizing/sterilising/sterilization/CSSD/recirculation/recirculating AND implant/screw/plate/orthopaedic/orthopedic
APPENDIX B: Microscopical images of new and reprocessed screws
Microscopical images of a new, unprocessed screw (top left image) alongside 2 images of screws that have undergone reprocessing on numerous occasions (images taken at 2 different magnifications).